driver silence callback

[Eliot Blennerhassett <linux@audioscience.com>]

Greetings,

Is the driver's silence callback meant to be able to *overwrite* some
part of the audio buffer that has already been written e.g. via the
playback *copy* callback?

In the case of my (older) hardware, once audio has been written via the
copy callback, it is gone (into a fifo), there is no way to overwrite
with silence.

The asihpi silence call back will _append_ a period of silence to the
already written audio queue.  I'm wondering if this is wrong?

Perhaps I should not have a silence callback at all?

I'm looking at the case in pcm_lib.c snd_pcm_playback_silence() where
"when runtime->silence_size >= runtime->boundary - fill processed area
with silence immediately"

My reference for silence callback.
http://www.alsa-project.org/~tiwai/writing-an-alsa-driver/ch11s02.html

regards

Eliot